Can Fluoridated Toothpaste and CPP-ACP Reduce Enamel Softening from pH-cycling?

Objectives: This study tests the effect of a fluoridated (F) toothpaste and a casein phosphopeptide amorphous calcium phosphate (CPP-ACP) paste in preventing enamel softening from an in vitro pH-cycling model with continuous replenishment of a remineralizing solution to simulate the washing effect of oral fluid.

Methods: Thirty-two specimens cut from eight bovine incisors were subjected to four days of pH-cycling (n=8). The pH-cycling consisted of an 80-min immersion in demineralizing solution three times a day. Between the immersions, specimens were placed under a drip of remineralizing solution which was continuously replenished at 0.1 mL/min. Group A received no treatment. Groups B, C, D received two daily applications of 2 min F-toothpaste (Crest, Procter&Gamble); 3 min CPP-ACP paste (Prospec™ MI paste, GC America); and F-toothpaste/CPP-ACP paste, respectively. Vickers hardness was measured at baseline and after the pH-cycling to calculate the change in surface hardness (DVHN). Statistical analysis of DVHN was determined using ANOVA and Student-Newman-Keuls test at 0.05 significance level.

Results: Enamel surface hardness of all groups significantly decreased after the four-day pH-cycling (paired t-test, p<0.05). DVHN (Mean ± SD) of Groups A, B, C, D were 224 ± 33, 75 ± 38, 201 ± 75, 105 ± 21, respectively. No significant differences in DVHN were found between Group A (no treatment) and C (ACP-CPP paste), and between Group B (F-toothpaste) and D (F-toothpaste/ACP-CPP paste). The decrease in hardness in Groups A and C were significantly higher than those in Groups B and D.

Conclusion: In this continuous replenishment model, F-toothpaste significantly reduced enamel softening after pH-cycling, whereas CPP-ACP paste alone did not. The application of CPP-ACP paste after F-toothpaste did not reduce enamel softening more than the application of F-toothpaste alone.

Supported in part by Minnesota Dental Research Center for Biomaterials and Biomechanics and Non-tenured Faculty Grant, 3M Foundation.